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Further reflection on the drogue shackle bolt issue leads me to ask this of the airworthiness and safety experts here. Was it sufficient for MB to deal with the known potential for shackle pinching by issuing maintenance guidance alone, and not doing anything more fundamental (such as introducing a shouldered bolt, reshaping the components, or even issuing a torque setting) to mitigate the issue? If it could be shown that a comparatively simple physical modification would have removed the accident mechanism, then would MB be open to a charge of negligence for not having taken such action in the 20-odd years between the risk becoming known and Sean's death?

TW50, agree it's odd to see the HSE becoming so prominent at military aircraft accident sites, not that they have a perfect right to be there, but they do seem to turn up quite often these days. I think that Scampton turned out to be a bit of a perfect storm with the MAIB, Police and HSE all appearing (with the Coroner pulling some of the strings too). Does it need all of them? Does it really help the efficiency of the process especially when other aircrew could also be at risk from a technical fault?

I know that the AAIB have negotiated a national agreement with the 43 UK Police forces on protocols for aircraft accidents, surely something similar could be sorted out for military accidents? Whatever happens, it's still a bit odd that the HSE feel they need equal billing in all circumstances. Maybe this is part of their motivation?

Was it sufficient for MB to deal with the known potential for shackle pinching by issuing maintenance guidance alone, and not doing anything more fundamental (such as introducing a shouldered bolt, reshaping the components, or even issuing a torque setting) to mitigate the issue? If it could be shown that a comparatively simple physical modification would have removed the accident mechanism, then would MB be open to a charge of negligence for not having taken such action in the 20-odd years between the risk becoming known and Sean's death?

I’m afraid the answer is not simple. The contractual relationship, if any, between MoD and Martin Baker needs to be known. MoD is obliged to put in place a continuous contract to maintain the build standard (which is what you’re talking about). This hasn’t been policy since at least June 1993 and it was fragmented for a few years before that. A key part of that contract is the delegation of financial powers to a named individual at the company, authorising him to self-task safety tasks, in the certain knowledge the company will be paid. The aim, of course, is to get crucial information out there as soon as possible. If there is no contract, there will be no task, and today 99.999% of MoD staff will give you a blank look when you mention this.

I’m not convinced MB did not provide the technical information/advice to MoD. This aspect has not been investigated at all and a key event was MoD shutting down its central registry and agency contracts that dealt with all such documentation. At a stroke, it meant that the process was no longer managed as a full-time job by a few, but as a 5 minutes, once a month task by hundreds. Without training. We got a few days notice of these changes and a party of us descended on the old registry to retrieve files before they were destroyed, only to find no sign of life, or filing cabinets. And no instruction was issued to companies telling them of any new department or address.

The same contract is the vehicle for maintaining the Safety Case. The Mk10 ejection seat didn’t have one, which points to a breakdown in this contractual relationship, as well as serial offences by MoD staff, who MUST have made false declarations in airworthiness documentation. (The HSE knows this, and says there is nothing wrong with it. I disagree).

One could say there is a moral obligation on the company, but an oft-asked, and never answered question was – how long must they be expected to work without payment? For example, MoD is obliged to provide Sample (or “Hack”) equipment, and often specialist test equipment, to companies under the above contract; and pay for their maintenance. As a matter of policy, AMSO started to run this down in 1990. I well recall that on the day Maggie Thatcher stepped down, I was at one company (Thorn-EMI Varian) and they handed an AMSO supply officer a letter asking which car park the MoD wanted over £2M worth of its test equipment dumped in. (Environmental Test Chambers, which had been rotting for over 2 years without maintenance). They were fed up subsidising MoD, and paying rent for storage. That TE was urgently required for Merlin development.

As to this specific case, I cannot say if the actions you suggest should have been a modification (or a Change), but your are right – either way one would expect Martin Baker to make a proposal to MoD. Who is to say they didn’t? Again, it became routine in 1990/1 for such suggestions to be ignored, because AMSO were just beginning to implement the policy of running down airworthiness management. One of the first instructions was not to amend APs. Alternatively, Martin Baker may have noticed the potential problem, but decided it was a procedural or maintenance oversight. After all, a maintainer should be expected to realise something is wrong if he’s tightening a nut and starts cutting thread on the shank of a bolt. Also, if trained on the mechanism, he should know it has to be free to move/swivel when assembled, and that a simple check of this is required. Martin Baker could, legitimately, claim that only an idiot would cut new thread and tighten it so much as to render it unfit for purpose. Part of the process is training and proper application. It is not for Martin Baker to stand over the maintainer and check his work. And, in any case, Martin Baker should be immediately absolved of any liability because of the illegal 50 hour RTI. The very fact this was implemented indicates either (a) there was no contract, or (b) specialist advice was ignored. Those familiar with the Mull of Kintyre case will see the resonance here. Odiham issued an illegal Servicing Instruction, probably because a request to have the design made safe was turned down. MoD has form here – Martin Baker does not.

I'm aware of at least one example where a PT officer seeing this scrubbed the item out of the contract saying that only a crown servant could authorise expenditure no matter how small the limit of liability. In effect the amount was just enough to decide whether any more effort would be required for further investigation.

Was it Def Stan 05-125 which contained this? I'm also aware of a discussion at NETMA about monitoring safety and airworthiness where the PT said "...but we do this". I can't help thinking that vague or misleading regulations contributed to the confusion. Possibly a mitigating factor in MBA's case?

Getting a bit more into the technical aspect of the shackle and bolt. I agree that, as stated early, It's very surprising that MB didn't design a bolt with a shoulder that the nut was tightened up against. I've been a dreadful aviation hoarder/scavenger for years and have played with plenty of MB products. The innovative design and build quality is staggeringly impressive. So the use of a 'normal' off the shelf bolt is very surprising. (I know MB probably made the bolt specifically.

I am slightly puzzled about the torquing up of a locknut & bolt where you don't want the nut to bottom-out on the thread or even against a fitting the bolt goes through. In other words you are purely relying on the resistance to the 'locking' ability of the nut. A brand new nut is invariably going to be stiffer than a well worn one. How do you calculate a torque that caters for both cases? Clearly, if a normal nut were used you could only achieve a tightening torque when the nut is up against the fitting! If the specified tightening torque is less than the resistance of a worn nut screwed along a continuous thread, then you can only achieve that value when the nut impinges on something else.

It makes you wonder what the MOD support contract was that was in place, for the aircraft I maintain you pay for the manuals and all updates, service bulletins etc, the only things you do not need to pay for are Airworthiness Directives which come from the CAA, FAA etc. I do wonder if the contract was all embracing, that could account for the RAF not getting some of the documentation other forces appear to have received.

Civi street wise we always replace lock nuts with new, RAF wise we used to check for run down torque resistance, you can measure that on a torque wrench..

As for a shouldered bolt, there might have been good reasons, such as the reduced diameter threaded portion if the bolt was shouldered not being of sufficient strength so as to not fail in the case of an ejection, and the main shank of the bolt not having sufficient clearance in the shackle for its diameter to be increased.

As for a shouldered bolt, there might have been good reasons, such as the reduced diameter threaded portion if the bolt was shouldered not being of sufficient strength so as to not fail in the case of an ejection, and the main shank of the bolt not having sufficient clearance in the shackle for its diameter to be increased.

Umm, possibly, but there must be a better design! If not, why not use an appropriate 'feeler gauge' type tool to place between the inside of the shackle and the scissor linkage to tighten the nut against that is removed once the nut has been correctly torqued.

Having spent many hours sat on both Mk3 and Mk 4 seats, the face-screen pin was always inserted 'blind'. Quite a test of dexterity, flexible limbs and a long reach! I recall in the JP when dual we did each other's pin.

The seat pin was also fitted blind, but then both pins visually checked upon leaving the aircraft.

......As for a shouldered bolt, there might have been good reasons, such as the reduced diameter threaded portion if the bolt was shouldered not being of sufficient strength so as to not fail in the case of an ejection, and the main shank of the bolt not having sufficient clearance in the shackle for its diameter to be increased.

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Nope. the shouldered bolt design had been in use for decades. My first encounter was in 1963 on JP Mk4 seats. Their use continued at least to Mk 9. Ejection forces would have negligible (if any) effect on the bolt which only serves to hold the drogues (same sizes) attached until the aircrew/seat separate.

Nope. the shouldered bolt design had been in use for decades. My first encounter was in 1963 on JP Mk4 seats. Their use continued at least to Mk 9. Ejection forces would have negligible (if any) effect on the bolt which only serves to hold the drogues (same sizes) attached until the aircrew/seat separate.

But the seat is designed for various types, perhaps the shouldered bolt previously used had reached its design limits on the later seats, seat weight, crew weight, ejection envelopes etc all will play their part. There could be a myriad of reasons to redesign it, and there must have been some, otherwise they wouldn't have gone to the expense and trouble of doing so, and by removing the waisted portion, one would have thought strength of the bolt was possibly one of them..

I do wonder if the contract was all embracing, that could account for the RAF not getting some of the documentation other forces appear to have received.

There are two things that come to my mind here: -

We are informed that other users had been informed many years previously about this problem. What was the process for informing them? Was SIL 704 a reissue of a previous communication, that the MOD/RAF had not noticed that it had not got?

What was the advice to the other users of the Mk10 seat and if this advice had been implemented by the RAF would this event have occurred? The other side of this question is did the advice to users required new parts to be put into the seats? If so, from a corporate governance point of view, how is it that MB did not notice that the MOD/RAF had not ordered any of these kits..

There's a third point to add - it's apparent that a number of people in the UK knew/know of the issues and I'd guess that more than one person who works/has worked on those seats, knows of the issues - why wasn't this alerted/raised back through a process to make safe the design?

Getting a bit more into the technical aspect of the shackle and bolt. I agree that, as stated early, It's very surprising that MB didn't design a bolt with a shoulder that the nut was tightened up against. I've been a dreadful aviation hoarder/scavenger for years and have played with plenty of MB products. The innovative design and build quality is staggeringly impressive. So the use of a 'normal' off the shelf bolt is very surprising. (I know MB probably made the bolt specifically.

I am slightly puzzled about the torquing up of a locknut & bolt where you don't want the nut to bottom-out on the thread or even against a fitting the bolt goes through. In other words you are purely relying on the resistance to the 'locking' ability of the nut. A brand new nut is invariably going to be stiffer than a well worn one. How do you calculate a torque that caters for both cases? Clearly, if a normal nut were used you could only achieve a tightening torque when the nut is up against the fitting! If the specified tightening torque is less than the resistance of a worn nut screwed along a continuous thread, then you can only achieve that value when the nut impinges on something else.

Although I have said it already I'll say again. That bolt was never meant to be fastened/unfastened all the time. For the Ist half (or more) of that seats life it's possible it was never undone. Work would only have been ever done in the seat bay and opening the shackle was done by releasing the BTRU. I would be interested to know who authorised 1st line rectification of ejection seats after the demise of seat bays. I would like to think this would have been discussed at MB and recorded decisions made.

Edit, a distant memory but I'm sure at servicing we tested the opening of the shackle we a spring balance measurement, had to be under a certain pull weight.

I'm aware of at least one example where a PT officer seeing this scrubbed the item out of the contract saying that only a crown servant could authorise expenditure no matter how small the limit of liability. In effect the amount was just enough to decide whether any more effort would be required for further investigation.

Was it Def Stan 05-125 which contained this? I'm also aware of a discussion at NETMA about monitoring safety and airworthiness where the PT said "...but we do this". I can't help thinking that vague or misleading regulations contributed to the confusion. Possibly a mitigating factor in MBA's case?

The PT officer obviously didn't know that the Def Stan was mandated in every aviation related contract. This delegation to Post Design Services Officers at Design Authorities is unique, and it was why MoD Technical Agencies (uniquely) are named in contracts, whereas otherwise it is simply the post title. The PT officer you mention almost certainly wasn't a properly authorised or qualified TA. He may have been "Suitably Qualified and Experienced" as defined by the MAA, but I can assure you this comes nowhere near the criteria for a TA, who (typically) will have worked on similar kit as a fitter/technician/ diag/supervisor, then been a design draughtsman or similar, engineering staff officer in an HQ branch, promoted into MoD(PE) and been manager of scores of projects. Only then would you be considered. However, I concede this has probably been diluted since my day!

Locknuts - 100% replacement. Given there are arguments for and against re-use, it is better to be safe than sorry, for the sake of a few pence. As a young planner/examiner, I'd have been crucified if I didn't specify new nuts every time. But at front line, I accept a concession might be occasionally necessary. I always thought of this in the same way as in-line splices, being a simple greenie.

Lock nuts in the RAF while I was serving were not mandatory to replace, you checked their run down torque, and were trained to do that, however I always did replace them and have ever since, I once had a cost conscious owner question me over it, I said I was replacing them end off, he then brought in a magazine article a few weeks later that had a rudder bar that came adrift because of it and the penny finally dropped.